1. Field of the Invention
This invention relates to an input device for inputting data from a keyboard, and more particularly relates to an input device which supplies a scanning signal to a key matrix of the keyboard checks the scanning signal returned from the key matrix and generates a signal corresponding to an operated key of the keyboard, a key roll-over function of the input device being improved.
2. Description of the Related Art
Keyboard devices for inputting key data are disclosed in U.S. Pat. Nos. 3,745,536 and 3,792,466, for example. In order to overcome a difficulty in the prior art in which, when three keys are depressed, the keyboard device responds as if four keys are depressed, the applicant has previously proposed a novel input device having a roll-over function to discriminate any new key, as disclosed in U.S. patent application Ser. No. 854,571, filed Apr. 22, 1986 now U.S. Pat. No. 4,833,447, issued May 23, 1989 and assigned in common herewith. The disclosure of U.S. Pat. No. 4,833,447 is incorporated in the present application by reference.
In the key matrix as described above, it may happen that, when three keys disposed at certain columns and certain rows of the keyboard are depressed, the key matrix responds in the same way as when four keys are depressed, and an erroneous data input is produced.